Oxidative Stress-Mediated Growth and Yield Decline in Groundnut under Nickel Toxicity: Physiological, Biochemical, and Genotypic Insights

Abstract Heavy metal contamination of agricultural soils poses risks to crop productivity and food safety. A controlled experiment evaluated the growth, physiological, biochemical, antioxidant, and yield responses of two groundnut (Arachis hypogaea L.) cultivars (GJG-9 and GJG-22) exposed to four nickel (Ni) concentrations (0, 20, 100, and 200 ppm). Measurements were recorded at 30 and 60 days after sowing and at harvest. Increasing Ni levels significantly (P ≤ 0.001) reduced plant height, biomass, photosynthetic pigments, membrane stability, and pod number, with greater reductions at higher concentrations. At 200 ppm Ni, pod number decreased by 30−45% compared with the control. Nickel stress enhanced hydrogen peroxide, malondialdehyde, proline content, and ABTS radical-scavenging activity, indicating oxidative stress and antioxidant activation. Roots accumulated more Ni than shoots, while translocation declined with increasing Ni. Cultivar GJG-22 showed greater tolerance than GJG-9, suggesting genotypic differences in Ni stress adaptation. These findings can facilitate breeding programs aimed at developing Ni-tolerant cultivars.